The sequences spanning 307 bp of the mitochondrial cytochrome b gene were determined for 45 sepcimens of Beryx splendens and seven specimens of B. mollis collected in Japan, resulting in identification of 11 and three haplotypes in the two species, respectively. The parsimony tree was constructed from the determined sequences and those registered into the GenBank database as species A and W of B. splendens collected in New Caledonia, featuring with two clades. The first clade comprised species W from New Caledonia and B. mollis in the present study, whereas the second one contained species A from New Caledonia and B. splendens in the present study. These results demonstrate a large geographic distribution for both B. splendens and B. mollis. Some of the haplotypes found in Japan were identical to those of New Caledonia for both B. mollis and B. splendens, suggesting levels of gene flow at the trans-oceanic scale.

NORFOLK 2

On evolutionary timescales, sea level oscillations lead to recurrent spatio-temporal variation in species distribution and population connectivity. In this situation, applying classical concepts of biogeography is challenging yet necessary to understand the mechanisms underlying biodiversity in highly diverse marine ecosystems such as coral reefs. We aimed at studying the outcomes of such complex biogeographic dynamics on reproductive isolation by sampling populations across a wide spatial range of a species-rich fish genus: the sergeants (Pomacentridae: Abudefduf). We generated a mutlilocus data set that included ten morpho-species from 32 Indo-West Pacific localities. We observed a pattern of mito-nuclear discordance in two common and widely distributed species: Abudefduf sexfasciatus and Abudefduf vaigiensis. The results showed three regional sublineages (Indian Ocean, Coral Triangle region, western Pacific) in A. sexfasciatus (0.6–1.5% divergence at cytb). The other species, A. vaigiensis, is polyphyletic and consists of three distinct genetic lineages (A, B and C) (9% divergence at cytb) whose geographic ranges overlap. Although A. vaigiensis A and A. sexfasciatus were found to be distinct based on nuclear information, A. vaigiensis A was found to be nested within A. sexfasciatus in the mitochondrial gene tree. A. sexfasciatus from the Coral Triangle region and A. vaigiensis A were not differentiated from each other at the mitochondrial locus. We then used coalescent-based simulation to characterize a spatially widespread but weak gene flow between the two species. We showed that these fishes are good candidates to investigate the evolutionary complexity of the discrepancies between phenotypic and genetic similarity in closely related species.

MADEEP, PAPUA NIUGINI

Previously confused with the small giant clam Tridacna maxima, the recently resurrected Noah’s giant clam, Tridacna noae, has been reported from the Taiwanese and the Ryukyu archipelagoes. Our recent underwater observations now extend its distribution to Dongsha (northern South China Sea), Bunaken (Sulawesi Sea), Madang and Kavieng (Bismarck Sea), the Alor archipelago (Sawu Sea), Kosrae (Caroline Islands), New Caledonia, the Loyalty Islands and Vanuatu (Coral Sea), Viti-Levu (Fiji), Wallis Island, and Kiritimati (Northern Line Islands). Published mitochondrial DNA sequences retrieved from open-access databases also indicate its presence in eastern Negros (Philippines), in the Molucca Sea, at Ningaloo Reef (Western Australia), and in the Solomon Islands. Noah’s giant clam is thus a widely distributed IndoWest Pacific species. Wherever research has been done on small giant clams throughout T. noae’s range, the inadvertent confusion of T. noae with T. maxima might have led to overestimating actual T. maxima densities and to errors in estimating demographic parameters.

KAVIENG 2014, PAPUA NIUGINI

Blainville’s beaked whale (Mesoplodon densirostris) was positively identified in the waters around New Caledonia from two strandings, one live sighting, and two rostra collected from the seafloor. This is the only species of Ziphiidae reported so far from the New Caledonian archipelago and adjacent waters.

BATHUS 3

Two sibling species, Beryx mollis and B. splendens, are potentially the main fish species of commercial interest for a bottom-line fishery in the deep waters of New Caledonia’s EEZ. Two datasets, morphological and meristic (one from Japan, the other one from New Caledonia) were obtained from specimen samples of the two species, which were species-identified by either the number of pyloric caeca (which allows total discrimination of the two species), or DNA markers, or a posteriori by the outcome of principal component analysis (PCA). Four morphological variables were measured (body height, head length, snout length, orbit diameter) and transformed to take standard length into account. None of these morphological variables, either single or combined to another, allowed sufficient discrimination between the two species. PCA on the four morphological variables led to a slightly better result, but still insufficient. Six meristic variables were utilized (numbers of soft rays in the dorsal, pectoral, pelvic, and anal fins, number of branchiospines on the lower half of the first branchial arch, number of scales on the lateral line). All these variables except the number of scales on the lateral line, proved useful to statistically distinguish the two species. However, none was diagnostic when taken separately from the other variables and the combination of two variables was only slightly better for this purpose. Canonical discriminant analysis helped determine which meristic characters could be used in priority to identify individuals: these were the numbers of soft rays on the dorsal, pectoral, and pelvic fins, and the number of branchiospines. In practice, if the fish is disembowelled or filetted, it takes only counting the number of pyloric caec for identification to species. If the fish is preserved whole before being marketed, then we recommend to count the numbers of soft rays on the dorsal, pectoral, and pelvic fins for a reasonably reliable identification.

HALICAL 1, NORFOLK 2

The large-eye seabreams or Monotaxinae is one of two subfamilies in the Lethrinidae, a family of perch-like coral reef fishes. Despite its widespread occurrence and its commercial interest in the tropical Indo-West Pacific (IWP), this subfamily has traditionally been considered a taxonomically difficult group. Based on 268 samples collected from all 15 known large-eye seabream species throughout their distribution ranges, we investigated the taxonomic diversity and phylogenetic relationships in the subfamily. From the results of multiple analyses on four gene markers, we confirmed the monophyly of all four genera in the subfamily (Gnathodentex, Gymnocranius, Monotaxis and Wattsia). We confirmed the occurrence of two species in the genus Monotaxis. We reported 15 delimited species within the most speciose genus Gymnocranius, four of which are potentially new species. The time-calibrated phylogenetic reconstruction enabled us to clarify the evolutionary history of the large-eye seabreams and to infer past patterns of species distribution. The most recent common ancestor to the Monotaxinae likely occurred in the central IWP ca. 32 million years ago. A burst of species diversification likely took place during the Mid- to Late Miocene, coinciding with tectonic change in the central IWP region. This gave rise to most extant lineages in Gymnocranius. The observed geographic distribution patterns in the subfamily most likely point to the central IWP as the area of origin and diversification. This was followed by multiple events of centrifugal range expansion towards either the Indian Ocean or the western Pacific Ocean, or both. Our results thus provide new support for S. Ekman’s center-of-origin hypothesis.

PAPUA NIUGINI

Aim: The unique biodiversity in the Red Sea is the result of complex ecological and evolutionary processes driven by Pleistocene climatic change. Here we investigate the species diversity, phylogenetic relationships and phylogeographical patterns of giant clams in the Western Indian Ocean (WIO) and the Red Sea to explore scenarios of marine speciation in this under-studied region.

ATIMO VATAE, INHACA 2011, KAVIENG 2014, PANGLAO 2004, PAPUA NIUGINI

Molecular markers allow insights into the population biology and ecology of deep-sea organisms, which are usually hardly accessible to direct observation and poorly known. Such a study was undertaken here for the deep-sea fish Beryx splendens, a species of growing interest to fisheries. B. splendens populations were sampled on seamounts and continental margins in the southwestern Pacific (New Caledonia, New Zealand, southeastern Australia) and in the northeastern Atlantic. Two hundred and fifty individuals were characterised by their single-strand DNA conformation (SSCP) of a z 360-base-pair (bp) fragment of the mitochondrial cytochrome b gene, amplified by the polymerase chain reaction (PCR). Two major SSCP haplotypes were observed in New Caledonia, a and w, whose frequencies were negatively correlated along a north-tosouth cline. All SSCP haplotypes in the total sample were sequenced on 273 bp. The phylogenetic tree of B. splendens haplotype sequences, rooted by two B. decadactylus sequences, showed that a and w belong to distinct mitochondrial clades, A and W, which are separated by z 4–6 % nucleotide divergence. Thirty individuals from New Caledonia were characterised by their DNA fingerprint from arbitrary-primed PCR. The distribution of individual-pairwise similarity indices was strongly bimodal. The larger similarity values all corresponded to comparisons within a clade (A or W) while the lower values were all between clades. Therefore, there was a strict association between the mitochondrial type and the DNA (presumably, nuclear DNA) fingerprint of an individual. Altogether, these results point to the existence of two biological species (sp. A and sp. W) within the current taxon B. splendens. No within-species differentiation was detected at the regional scale (New Caledonia). A remarkable result is that the three cytochrome b haplotypes of northeastern Atlantic B. cf. splendens sp. A were also the three commonest in the southwestern Pacific populations of this species. Such a level of homogeneity in the distribution of haplotypes suggests there is, or recently has been, gene flow at the inter-oceanic scale.

HALICAL 1, HALIPRO 2